/**
 * Returns a color value for a $tone from a defined $palette.
 * @param  {String} $palette         Name of palette.
 * @param  {String} $tone:   'base'  Name of tone, default to `base`.
 * @return {Misc}                    Color value.
 */
@function color-get($palette, $tone: 'base') {
  @if (map-has-key($COLORS, $palette)) {
    $palette-map: map-get($COLORS, $palette);
    @if (map-has-key($palette-map, $tone)) {
      @return map-get($palette-map, $tone);
    }
    @else {
      @error 'Tone `#{$tone}` doesn’t exist in palette `#{$palette}`';
    }
  }
  @else {
    @error 'Palette `#{$palette}` doesn’t exist';
  }
  @return false;
}